## Classes

```js
class Circle extends Shape {
// Constructor
  constructor (radius) {
    this.radius = radius
  }
 
// Methods
  getArea () {
    return Math.PI * 2 * this.radius
  }
 
// Calling superclass methods
  expand (n) {
    return super.expand(n) * Math.PI
  }
 
// Static methods
  static createFromDiameter(diameter) {
    return new Circle(diameter / 2)
  }
}
```